Hadley, Behavior of the A^nerican Lobster. 



269 



formed by A with the horizontal. When the angle was slight 

 the forward rotation of the larva was but a few^ degrees, and it 

 continued to swim in this body-position, and might undergo a 

 positive or negative progressive orientation, as ordinarily. When, 

 however, the angle between A and the horizontal was greater, the 

 degree of rotation of the larva was proportionately greater, and 

 in certain cases it might undergo a rotation of 180° and fall to 

 the bottom. 



When, on the other hand, the incident rays struck the larva in 

 the direction of C (Fig. 16), then the larva underwent a backward 

 rotation whose degree was dependent upon the breadth of the 



Fig. 16. For description, see Case 4. 



Fig. 17. For description, see Case 6. 



angle between C and the horizontal. If the angle thus formed 

 was slight, the backward rotation of the larva was correspondingly 

 slight, and it would continue to swim in the position designated 

 C (Fig. 16), undergoing positive or negative progressive orienta- 

 tion as other conditions of light might determine. If the angle 

 formed between C and the horizontal was great, the degree of 

 backward rotation of the larva was proportionately greater, and 

 a fall to the bottom, tail downward, might result. 



Corollary I — When the direction of the rays w^as determi-ned 

 by compounding the vertical series of light factors (A, B, C, Fig. 

 12) with the horizontal series (a, h, c, Fig. 15), the resulting reaction 

 was a combination of the two types of behavior described above. 



